1. Field of the Invention
The present invention relates to a traveling mechanism for a lifting device which is movable on rails, particularly for a lifting device having a laterally cantilevering boom.
2. Description of the Related Art
A traveling mechanism of a lifting device which is movable on rails is known from the brochure "Kranbaukasten KBK [KBK Crane Building Blocks]" by Mannesmann Demag Fordertechnik AG. This prior art traveling mechanism has running wheels which run parallel to one another in pairs one behind the other in the traveling direction. The running wheels roll within an interior of a downward-opening hollow-section rail of an overhead track on substantially horizontal inner running surfaces of the rail. The running surfaces extend in the longitudinal direction of the rail and are sloped relative to one another. To attach a load, a connection element is connected with axles of the running wheels. The connection element projects downward out of the rail for attachment to the load to be carried.
These traveling mechanisms with the associated adapted rails are also suitable for the operation of pillar and wall-mounted swiveling jib cranes, monorail systems and suspension cranes.
The rails are optionally combined with one another and are assembled by automatically centering plug-in and screw connections. The horizontal forces occurring as a result of buffer stroke or approach procedures and braking processes are substantially absorbed by a pendulum type suspension of the interconnected rails.
A disadvantage in these known traveling mechanisms and rails consists in that, although they are very well suited for use with pendulum type suspensions, these traveling mechanisms are severely worn or even destroyed when used with a rigidly suspended rail which is required for absorbing and diverting upwardly directed forces due to regularly occurring horizontal forces. The horizontal forces prevent smooth ruing of the traveling mechanisms inside the rail. The upwardly directed forces cannot be absorbed and transmitted in the pendulum-like suspension, making the pendulum-like suspension unsuitable for laterally cantilevering booms of two-rail cranes.